2.7 For almost 70 years the standard treatment has been clipping of the aneurysm through an open operation (craniotomy). Initially this carried a very high mortality but over the years improvements in surgical and anaesthetic techniques, together with improved equipment and better peri-operative care have improved outcome. 2.8 During the last 10 years neuroradiologists have been developing a technique of packing aneurysms with platinum coils through a vascular catheter introduced into an artery in the groin. This does not require opening the skull. 2.9 The MRC funded “International Subarachnoid Aneurysm Trial� (ISAT) was undertaken to compare the two forms of treatment. 3.
What was known before ISAT?
3.1 In spite of improvements in outcome over the years, many people are left disabled or dependent following aSAH.3 3.2 In published studies there is a wide range of quoted surgical outcome with variation between and within centres. Some of this might depend on case mix, availability of resources or colleagues, but it is likely that at least some is related to the skill of the individual operator.6,7 3.3
Outcome appears to depend upon -surgical experience8,9 -institutional volume of craniotomy for aSAH10,11 -ability to offer both neurosurgical and endovascular treatment12 -ability to offer angioplasty for ischaemia12 -specific neuro intensive care facility13 ,14
3.4 Coiling is the treatment of choice for most posterior circulation aneurysms.15 4.
ISAT1
4.1 An International, multi-centre, randomised trial comparing outcome after surgical treatment (clipping) with outcome after endovascular treatment (coiling). Most Centres were in the UK. 4.2 To be included patients had to have unequivocal evidence of aSAH. In the opinion of the participating neurosurgeon and neuroradiologist either treatment would have been possible and there was no reason to prefer one over the other. Inclusion was only possible if informed consent was given. 4.3 Centres were only permitted to take part in the trial if the radiologist(s) had already performed at least 30 coiling procedures.
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